Dave58er
Senior Member
- Location
- Dearborn, MI
Hi all. I'm looking at plans for a laundromat and there are some irregularities with the load calculations as far as I can tell. I'd like to back up and just do the calculations from scratch, develop load totals based on part II of 220, and apply the demand factors. But the way they calculated has me second guessing if I would be doing it right, so I am hoping to get some feedback from some people with more experience in this area before I do so.
One part that keeps messing me up is the phasing. The service is a three phase 208/120. The first panel is three phase, but then there is a sub panel (Panel B) that is only 208 single phase. All the dryers are fed off this sub panel. The part I am not sure about is do I just calculate all the loads in the building like normal, then divide the va by voltage x 1.73 like I would if everything is balanced? Because the two phases feeding the sub panel will be significantly higher in amperage then the remaining phase that is only used in Panel A.
Another concern I have is that where the load of Panel B (which is single phase 208) is calculated before being added to the load for Panel A it is divided by 1.73. I thought that was only appropriate for three phase loads. Am I wrong about that?
And yet another concern I have is that all of the washer and dryer loads, which the print has totaled under "equipment" are added together to get a raw number and then multiplied by 65%. I'm guessing this is some sort of demand factor, but I don't get where you can take the nameplate of equipment and multiply it by a demand factor in this scenario.
An additional kicker is that the Load for panel B (which is divided by 1.73 even though it is single phase), is added to the loads of Panel A, totaled with them, and then divided by 208 x 1.73 again. Even if you could divide it once, I don't see how it would be legitimate to divide it again.
I greatly appreciate any feedback you can provide.
One part that keeps messing me up is the phasing. The service is a three phase 208/120. The first panel is three phase, but then there is a sub panel (Panel B) that is only 208 single phase. All the dryers are fed off this sub panel. The part I am not sure about is do I just calculate all the loads in the building like normal, then divide the va by voltage x 1.73 like I would if everything is balanced? Because the two phases feeding the sub panel will be significantly higher in amperage then the remaining phase that is only used in Panel A.
Another concern I have is that where the load of Panel B (which is single phase 208) is calculated before being added to the load for Panel A it is divided by 1.73. I thought that was only appropriate for three phase loads. Am I wrong about that?
And yet another concern I have is that all of the washer and dryer loads, which the print has totaled under "equipment" are added together to get a raw number and then multiplied by 65%. I'm guessing this is some sort of demand factor, but I don't get where you can take the nameplate of equipment and multiply it by a demand factor in this scenario.
An additional kicker is that the Load for panel B (which is divided by 1.73 even though it is single phase), is added to the loads of Panel A, totaled with them, and then divided by 208 x 1.73 again. Even if you could divide it once, I don't see how it would be legitimate to divide it again.
I greatly appreciate any feedback you can provide.
